Regarding your question on what needles to use with what fabric.

60/8 Universal - silk, organza, chiffon, sheer

70/10 Universal - Blouse & lightweight dress fabric

70/10 Microtex - Batiste, crepe de chine, microfiber

75/11 Stretch - Interlock knit, lycra

75/11 Quilting - Quilting through various batting

80/12 Embroidery - rayon thread for decorative stitches & embroidery

80/12 Universal - Cotton, linen. wool

80/12 Metallic - Metallic & decorative thread

90/14 Jeans - Denim, canvas

90/14 Stretch - Fleece, knit, faux suede & leather